Helminthiasis, the infestation of an animal by certain species of parasitic worms, is one of the most common, serious and widespread animal diseases. Helminthiasis is a serious economical problem in domesticated animals such as swine, sheep, cattle, goats, dogs and poultry. The most common genera of nematodes infecting the animals referred to above are Haemonchus, Trichostrongylus, Ostertagia, Nematodirus, Cooperia, Bunostomum, Oesophagostomum, Chabertia, Trichuris (whipworm), Ascaris, Capillaria, Heterakis and Ancylostoma. Certain of these, such as Trichostrongylus, Nematodirus and Cooperia, attack primarily the intestinal track while others, such as Haemonchus and Ostertagia, are more prevalent in the stomach.
The above parasites during their maturation and growth have a very deleterious effect upon the animal and its rate of growth. In the intestine, and stomach, the parasites erode the epithelial tissues bringing about hemorrhage, anemia, weakness and tissue necrosis. Animals if they do not succumb to gross parasitism, are rendered economically unfit by weakness, lower vitality and poor growth and reproduction. The economic loss to the cattle, sheep and poultry industry of the United States from gross parasitism is extremely high.
While many drugs have been developed to try and offset the effects of these diseases, they have not been completely satisfactory for a variety of reasons. In some cases the drugs have not been sufficiently effective, and in others the cost of the drug has been too high and in many cases the parasites have developed a resistance to the drug.